Lecture 12: Sex Differences in Stress Flashcards
Sex differences in health
Heart disease M > F Depression F > M Alzheimer disease F > M Addiction M > F Autoimmune disease M < F
As these often have links to stress, this implies there might be stress differences by sex
Sex bias in research
Often use males including male animals
Female hormones are complex and can confound
But this messes up external validity
Now trying to not do this again
ACTH in response to TSST
Males have higher ACTH response
-Females similar regardless of cycle phase
- THIS experiment shows luteal phase women to have drop off quicker
- Follicular less neg feedback?
Salivary free cortisol in response to TSST
ACTH corresponds to FREE cortisol
-Higher in luteal phase than follicular
Males = bigger response
-Lower free cortisol in luteal phase (might result in les binding and explain less negative feedback)
Total Plasma Cortisol in response to TSST
Any negative feedback on production of ACTH is through cortisol binding
- Total plasma cortisol includes that which cannot bind
- So there is no correspondence between Total blood cortisol and ACTH
OC pill has high total plasma cortisol
Maybe cyclic hormones’ contribute to binding globulins
Higher levels of binders in OC pill use and so overall high levels of cortisol (does not mean it is free)
Sex Differences in Stress Redux
Men exhibit greater stress reactivity to TSST
By both ACTH and cortisol
BUT
Women report MORE subjective stress
- Possibly societal constraints on men?
- Possibly the nature of the stressor, effects of social support, and timing of cortisol measures….
Does the nature of stressor matter?
Manipulation of panel sex in TSST
G1 2 men on panel
G2 2 women on panel
-When evaluated by men, men had no cortisol response
-When women did the test, they had no cortisol when it was women
THIS TIME women in the luteal phase showed no response and women in the follicular phase did
Maybe the way the cycle was measured was different
RESULTS
- TSST response in the follicular women
- Opposite effect to previous results – cycle measured differently
- Judgement by opposite sex more stressful
- Men and women both more stress when scrutinized by opposite sex
TSST non responders
In both sexes, some people do not respond to the TSST
Individual differences
Does the nature of stressor matter?
Modifying the TSST to exclude someone
TSST is the gold standard for inducing stress in the lab
- Evaluates performance under pressure
- Men exhibit greater stress response
MODIFICATION
-Social rejection stress
Two confederates gradually exclude participant
- Social support more important for women
- Stress response?
RESULTS
Types of stressor does matter
-Men exhibit expected response to TSST
BUT
-Women show elevated cortisol to social rejection stressor while men do not
-Also slower cortisol response in women vs men
(perhaps because it takes a while for the participant to realize they are being excluded socially
-Less ACTH but less GR as well
Does the nature of stressor matter?
Modifying the TSST Manipulating social-evaluative threat by moving the panel in and out of the room
Move panel that evaluates the participant in and out of the room
In both cases, the panel is still evaluating you but you cannot see immediately that they are doing so if they are outside
When they did the trial in men they varied the size of the panel too
The main thing is the public speaking that stresses in this trial
RESULTS
In men
- Does not matter about the size of the panel
- Does not matter if the panel is present or not
In women
-If in the room = more stress
Modulating social component of stressor affects women
No effect on men, even with more manipulations
TSST revision
(1) Men have more ACTS and Cortisol response
(2) Women do have a stress response, just lower
(3) Menstrual cycle effect is unclear
(4) This is affected by the sex of the panel (more stress for opposite sex)
(5) This is affected by the social nature of the stressor
For men, the performance is the stressor
For women, it is the social content
Tend and Befriend
Novel theory on stress response
Fight or flight: Male
Tend and befriend: Female
Reflects the evolutionary necessity for differing stress responses
Women were responsible for caring and farming so the stressors they experienced are different. Fight or flight does not help one survive a flood but cooperation might
Incomplete Evolutionary Analyses.
Suggests few sex differences due to common threats
Fight/Flight seems to fit major threats
BUT…..there are other challenges humans faced
What about less immediate threats?
What about managing offspring?
Fight or flight cannot solve this
Shelley Taylor from Harvard, 2000
Additional stress response developed for women’s responsibility
Women:
TEND:
Quieting and caring for offspring.
Get infant out of harm’s way.
BEFRIEND:
Create social networks to provide resources and protection for self and infant.
Oxytocin
Hormonal response to stress differs in men and women
Tend-and-Befriend (oxytocin)
-Higher levels of this in women
Strong behavioral evidence and cross species communality
-Contributes to stress response
Any evidence for this in men?
Neuroendocrine Basis: Tend and Befriend
OXYTOCIN (Women > Men)
- Released during stress and enhanced by estrogen
- Reduces activation of SNS and HPA systems
- Decreases cortisol & adrenalin
- Reduce stress response in men too
-Oxytocin injections increase maternal behavior, physical proximity to others, grooming (in monkeys)
- Breastfeeding mothers have reduced stress
- Lower cortisol and cardiovascular response to stress
-When block oxytocin women spend less time with friends
- Oxytocin affects numerous dopaminergic brain regions
- Makes these social contacts rewarding, reinforce behaviour
